Topical fluoride: Work will continue on optimizing the conditions so they will be clinically acceptable. Etching technique: Conditions will be sought which will increase the porosity of the etched surface while minimizing overall dissolution of the enamel surface. Tests will be made on the effects of our fluoride treatment on the strength of adhesion of the sealant. Remineralization of white spot: The use of aclcium phosphates such as Ca4 (PO4)2 O, alpha-Ca3 (PO4)2, Ca5(PO4)2SiO4 will be tested alone and in combination with CaHPO4 .2H2O and CaHPO4. Enamel solubility: Further work will be carried out, preferably in cooperation with clinician, in an attempt to correlate thermodynamic solubility with (1) caries experience, (2) exposure to fluoridated water, and (3) source of tooth. Bone solubility: An attempt will be made to develop a procedure for measuring the "solubility spectrum" of bone samples. Mechanism of dental caries: Work will continue on trying to identify the important parameters in the caries process. In particular, experiments will be carried out to determine how cationic and anionic surfactants and permselective membranes affect the caries process.